Apparatus for profiling bonding needles

ABSTRACT

In the bonding of a conductive wire to an electrical apparatus, the wire runs down through the hole in a hollow needle and extends at an angle of about 90 degrees with the needle at the tip thereof and the wire as it exits from the needle is bonded to a bonding pad comprising part of an electrical apparatus by a combination of pressure and heat. If the inside and outside profiles of the tip of the hollow needle are not properly rounded, bad bonds will result in that the wire may break. Polishing means are disclosed for giving the tip of the needle a proper smooth and rounded profile both internally and externally.

United States Patent mi 11 1 3, ,9

Da Costa et al. 1 1 Apr. 29, 1975 i541 APPARATUS FOR PROFILING BONDING 8$X.MS 711907 Morris 51/154 NEEDLES i751 lnventors: Harry Da Costa. Scottsdale: Charles Pnmml" """'P Kcucy Therm. Phmnix hmh AfiL Attorney. .{evmr or lUIll-VlllCClll J. Rauner; Michael i D. Bingham 1 i731 Asstgnee: Motorola. loo. Franklin Park. Ill. I 22 Filed: Feb. 21. 197.3 57 ABSTRACT 12H Appl. No.: 334.332 In the bonding of a conductive wire to an electrical apparatus. the wire runs down through the hole in a Rem! Apphcamm Dam hollow needle and extends at an angle of about 90 delbll Division of Ser. No. N .52 June 19. W71. Pat. No. 3.768.2l l. which is a division of Ser. No. 85 Ll33.

8.61 1x 969 p N M 64 it exits from the needle is bonded to a bonding pad comprising part of an electrical apparatus by a combi- Q nation of pressure and heat. lf the inside and outside a: 5. profiles of the tip of the hollow needle are not propg 4 M erl rounded bad bonds will result in that the wire may break. Polishing means are disclosed for giving the tip of the needle a proper smooth and rounded 5o References Cited l 1 profile both internally and externally.

UNITED STATES PATENTS minus slums SCl'lflttlCf sum x 3 Claims} grees with the needle at the tip thereof and the wire as APPARATUS FOR PROFILING BONDING NEEDLES CROSS REFERENCE TO RELATED APPLICATIONS This application is a division of application Ser. No. l56.523. filed June 29. l97l. now US. Pat. No. 3.768.2l l. issued Oct. 30. i973. which is a division of application Ser. No. 859.l 33. filed-Sept. I8. 1969. now US. Pat. No. 3.63l.645 issued Jan. 4. i972.

BACKGROUND This invention relates to means for giving the tip of a hollow needle-used in wire bonding a proper profile. In making connections to electrical apparatus such as that applied to chips. a bonding wire having a diameter 7 of a little less than 0.00l5of an inch may be used. This bonding wire is fed through a hollow needle and the portion thereof just outside the tip of the needle is bent over at about 90 to the needle. The needle is then pressed down onto a point on the bonding pad of the electrical equipment to which the wire is to be connected and the wireat the bend thereof is bonded to the electrical apparatus by a combination of pressure and heat. The needle and the apparatus are moved with respect to each other toanother point where'the wire is to be bonded and the bonding process is repeated. Wire is drawn down through the hollow needle-during the process of moving the needle and the apparatus with respect to each other. The needle is thendrawn alittle further and the wire may be cut off or the wire may be broken by rapid vibration or oscillation of the needle. leavinga long enough tail 'of wire extending from the tip of the needle so that another bond can be made. The shape of the tip of the needle is critie'al since in the process of bonding'due to'the pressure applied thereto. a groove or indentation or. impression is made in the wire during the'bonding whereby the wire takes on the shape of the tip of the needle. lf the tipof the it is an object of this invention to provide means for preparing the tips of new bonding needles or for repair ing the tips of worn or defective bonding needles.

SUMMARY In accordance with the invention. a hollow needle may be prepared for shaping by lapping the tip thereof to provide a tip that is perpendicular to the length of the needle. The tip of the needle is shaped by projecting particles of abrasive material towards the tip of the needle generally in directions parallel to or slightly divergent from the direction of the axis of the needle. Then the tip of the needle is polished by embedding the needle in an abrasive material and rotating the needle while so embedded. The. profile of the inside and the outside of the tip of the needle is observed by making an impression of the tip of the needle on a material such as the edge of a block or such as a wireso that the 'shape of the needle through the center portion of the tip thereof or along the plane through the axis thereof may be observedby observing the impression made thereby? DESCRIPTION The invention'will be better understood upon reading the following description in connection with the ac- @com'panying drawing in which:

I f-l6. l 'andZ are par tial crosssectional views of a needle taken at a plane'through the axis thereof.

FIG. 3 is an elevatioi t'al view of an abrasive blasting apparatus for shaping the tip of the needle of FIG. 1.

HO. 4 is an elevational view oi a' polishing apparatus 1 for polishing the tip or the needle of FIG. 1.

needle is not properly smoothed and rounded. the wire bondmay be defective inthat the wire may break at the t indentation when force is applied to the wire during the process of moving the needlewith respeetto the a'pparates or during the process of intentionallycutting or breaking the wire or during any otherfprocess. such as encapsulation. that may-take place. The-tipfof the neeit having an outside diameter of about Q .004

dle is tiny. of an inch and an inside diameter of about 0.00l5 of an inch. The profile of the tipatthe inside off the needle of the apparatus .of FIG; 8.

PK]. 5 it\ cr0ss-sectional ,view of theabrasive pad of HQ. 4 and showing the relative position of the needle and the abrasive p'ad during polishing operation.

FlG. 6'i s'jan elevational view of an apparatus for making an impression of the profile of the tip of the needle preparatory to -viewing it. i

" lG. l isaniill ustration of the profile obtained by using'th'e'apparatus of FIG. 6.

H HO. 8 is a partialelevational view of a modification of the apparatus of FlG.'6. and

FlG. 9 is an illustration of the profile obtained by use ."A known method f bo ding a wire 10.see FIG. 2.

' toabondin'g'pad "is to run the wire 10 through the hollow 12 of a" hollow needle "14' and bend the wire 10 s6 as'it exits from-theitip of the needle-'lfi jat' a 90 angle "with theieitgth'bfthe needle letThe needle 14 is then down'on' the bonding pad 1l;'and-.-.by a combicannot clearly be seen by the nakedeye or by the aid Q of optical instruments. Therefore. the only way one could be sure that a new needle had a proper tip profile was to try to make bonds with it and if. thebonds made thereby were good then the needle had 'a proper tip profile. Furthermore. the only waythat one couldkno'w that a needle was worn out waswhen this needle began making ba'd bonds. Furthermore. repairing 1. renewing --nation 'ofjh eitt and"pressure.'thewire l0 isbonded to the bonding pad 11. Due to this pressure. an impression 20 is formed in the portion of the wire l-0that is under the tip l6 of the needle 14. Then. the needle and the bonding pad 11 are moved with respect toeach other until another bonding pad'tnot-shown) is under the needle -14 and't'teedle-M is pressed down on the other the needle was a cut and'try method whereby needles were usually discarded when they began tomalte bad bonds. The cost of-diseardedlbad electrical apparatus produced by bad bonding. needles and the cost "of 'replacement of bad bonding needles added substantially to the cost of producing acceptable'electrical appara--.

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bonding padQwhereby a connection is provided between thetwo bonding pads. Then the wire it) is cut or is broken by'vibrating'the needle-l4 and another connection maybe made in a similar manner.

.lf the impressipn 20 in. the' wire IO-made by the needle. ldiis not.rpuridedzand smoo thed .}th'at is.=if the impression;

agged or. angular. the"wire .10 may break 'away-fro'rn it; bonding pad ll or it'may break between the two bondingp'ads to which it is connected during amt 'ter processing of the electrical apparatus. that is. if the. hp profile of the needle M is not smooth and rounded. the bonds made by the needle 14 may not be reliable.

The tip 7 of the needle 14 has a diameter of about 0.004o'f an inch and the inside diameter of the hole through the needle is about 0.005 of an inch. While it is possible to see the outside profile of the tip 18 with proper optical instruments. it is not possible to see the profile of the inside portion of the tip 18 in the vicinity of the hole 12 through the needle 14. The needles 14 when bought new may thereforchave ajagged or rough inside profile. Therefore. when new needles are bought they are treated as if their inside profiles are bad. They and used needles that have begun to produce bad bonds are treated alike.

New'necdles 14. sec HO. 1. as received. as well as used needles 14, are lapped in a known manner to produce a square tip 22. That is. after lapping. the tip 22 comprises'a plane which is perpendicular to the length of the needle 14.

Then the needle 14 is put in a chuclt 24 on a shaft 26 which is rotated by a motor 28 at a few hundred revolutions per minute and an abrasive material such as aluminum oxide particles 30 having diameters of from S to 30 microns is blown or projected directly at the tip of thc'ncedle l4 as from a nozzle 32 which is about 3 inches from the tip of the needle for from to '60 seconds depending on the size of the abrasive particles. A housing 34 may he provided to prevent scattering of the abrasive particles.

After being exposed to the abrasive blast for the required length of time. the needle 14 is talten out of the chuck 24 and put into a chuck 36 which is rotated by a motor 38 at several thousand revolutions per minute. An abrasive pad 40 is provided which may be a straight grained block of wood impregnated with diamond dust. the grains of the wood pad 40 being parallel to the axis of the needle 14. Then pad 40is fixedly mounted on a shaft 44. The ,shaft 44 is slideably and rotatably mounted in the bearings 46 and 48..A plate 50 is'fixed to the shaft 44 between the bearings 46 and 48. A circular plate 52 is fixed to a shaft 54 which extends per pendicularly to the shaft 44. The shaft 54 is rotated in 'a bearing 56 at about l0 rpm by a motor not shown.

The circular plate 52 has a projection or lobe 58 projccting from the periphery of the plate 52. The shaft 44 and the plate 50 as well as the pad 40 slide downward with respect to the bearings 44 and 46 due to gravity until the tip 18 of the needle 14 is embedded in the stationary pad '40 asshown in FIG. 5. The periphery of the plate 52 (except for the lobe 58) does notcontact the plate 50. Since the needle is rotating at high speed and since the tip [8 of the needle is cmbeddedin the straight grained pad 40. a portion of the pad-40 penetrates into an hollow 12 of the needle 14 and-both the outsideand the inside profile of the tip 18 of the needle 14 is polished by the pad 40. For each revolution of the shaft 54 and the platc 52. the projection 58. by its contact with the platc SO, lifts the pad 40 off of the needle l4 and rotates the pad 40 a small amount and then drops the pad 40. whereby the pad 40 presents new polishing positions to the needle 14 at periodic intervals depending on the speed of rotation of the shaft 54. After a few minutes in the polishing machine illustrated in FIGS. 4 and 5. the treatment of the tip 18 of the acedlc I4 is completed and the tip 18 is observed. As noted bonding tool-having above. due to the small size of the tip 18 of the needle 14. the inside of tip 18 cannot be observed directly. An apparatus for indirectly observing the needle tip 18 is shown in FlG. 6.

The needle 14 is held as in a clamp 60 comprising two parts 62 and 64 which are bolted together as by bolts and nuts 66. The needle 14 may be slid up and down on the rods 68 and 70 as by a handle 72 to cause contact of the tip 18 of the needle 14 with the junction of two soft blocks 74 and 76. The blocks 74 and 76 are held in a vise 78 by turning a thumb nut 80 and the junction of the blocks 74 and 76 can be moved to be in exact line with the axis ot the needle 14 by turning the screw 84 by means of a thumb nut 82, which causes lateral motion of the vise 78. An optical instrument (not shown) may be used to help align the junction of the blocks 74 and 76 with the needle 14. When the necdle 14 is pressed down. an annular groove or impression (not shown) is formed. one-half in each of the two bloclts'74 and 76. Then. when the blocks 74 and 76 are removed from the clamp 78, the edge of the grooves and 92 (see FIG. 7). may be examined by the eye. with the aid of an optical instrument if desired. to make sure that the grooves 90 and 92. and therefore the shape of the tip of the needle 14. are smoothly rounded off. if it appears necessary. the needle 14 may be turned 90 about its axisand another impression of the tip 18 thereof may be taken.

if desired. a wire 94 may be laid on the top of a block 96 in a groove 98therein. The wire 94 may be fixed to a pin, 100 which projects from the front of the block 96. The wire 94-may be lined up with the needle 14 (not shown in FIG. 8) by turning the screw 84 by means of the thumb nut 82. The diameter of the wire 94 is about equal to the diameter of the hole 12in the needle 14. When the alignment of the needle 14 and the wire 94 is complete. the axis of the needle 14 and the axis of the wire 94 intersect. these axes being at right angle to each other. When the impression of the tip 1 8 of the needle is made into wire 94 as by the means shown in FIG. 6. the grooves or impressions in the top of the wire 94. see FIG. 9. may be examined for smoothness of curvature by any suitable optical means. If the smoothness and curvature are not suitable. the needle 14 may be reprocessed as noted above.

A method and an apparatus for shaping the outside and the inside curvature of the tip of a hollow needle which is so small in inside diameter that the inside diameter cannot becheclted by known optical means has been disclosed. V a

What is claimed is: r J g I I. An apparatus for simultaneously polishingthc inner and outer-surface profiles of a tip of a hollow a body axially of the tip comprisng; l u a v means for holding and rotating the bonding tool about a first axis; polishing means having an axis of rotation spaced from and parallel to said first axis and including a grained pad impregnated with a polish material with said grains of said pad oriented parallel to said first axis for simultaneously polishing the inner and outer surface profiles of the bonding tool;

means for intermittently and alternately rotating said polishing-means including said pad along and about its axis; and

means further includes:

an additional bearing; an additional shaft extending perpendicularly to said shaft of said polishing means and said additional shaft being mounted in said additional bearing;

an additional circular plate fixed to one end of said additional shaft. said additional circular plate having a lobe projecting from the periphery thereof: and means for rotating said additional shaft at a lower number of revolutions per minute than the number of revolutions per minute of rotation of said means for rotating said bonding tool.

Q i i i 

1. An apparatus for simultaneously polishing the inner and outer surface profiles of a tip of a hollow bonding tool having a body axially of the tip comprising: means for holding and rotating the bonding tool about a first axis; polishing means having an axis of rotation spaced from and parallel to said first axis and including a grained pad impregnated with a polish material with said grains of said pad oriented parallel to said first axis for simultaneously polishing the inner and outer surface profiles of the bonding tool; means for intermittently and alternately rotating said polishing means including said pad along and about its axis; and means for embedding the tip of the bonding tool into said grained pad of said polishing means.
 2. The apparatus in accordance with claim 1 wherein said polishing means further includes: a pair of bearings; a shaft slideably and rotatably mounted in said plurality of bearings; a straight grained block of wood, with said grains oriented parallel to said first axis, connected to the end of said shaft; and a circular plate fixed to said shaft between said pair of bearings.
 3. The apparatus of claim 2 wherein said means for intermittently and alternately rotating said polishing means further includes: an additional bearing; an additional shaft extending perpendicularly to said shaft of said polishing means and said additional shaft being mounted in said additional bearing; an additional circular plate fixed to one end of said additional shaft, said additional circular plate having a lobe projecting from the periphery thereof; and means for rotating said additional shaft at a lower number of revolutions per minute than the number of revolutions per minute of rotation of said means for rotating said bonding tool. 